Booster Shots

High Hopes for a Tall Child? Check the Growth Charts

If you want to know how big a puppy's going to get, popular wisdom tells you to check out the size of its feet. But how do you tell how tall your kids will be? Do their pixie toes or clodhopping stompers offer a tip?

Science has taken a stab at the height-prediction issue, though. (How could it be otherwise, given how preoccupied we humans can be with stature, with being tall enough/short enough/just-right enough to get the boy, get the girl, get along in life?) The result is various calculators and formulas--even atlases of the slow, steady changes in kids' bones as they grow. But there's a lot of slop in such predictions, as much as several inches in either direction.

"I tell parents ... we can do it for fun, but don't place any bets on it," says West Hills pediatrician Christopher Tolcher.

Here, in any case, are a few ways that doctors do their guesstimating. Simple methods are based on the fact that genes play a big part in height. If Mom is tall and Dad is tall, then Junior (all things being equal) will likely be tall as well.

The methods also take into account that men, on average, are taller than women.

So if you want to know how tall your Sally will be at 18 (excluding any Mohawk hair spikes she may be sporting by then), calculate the average of Dad's height, minus 5 inches, and Mom's height.

And your Sammy? Take the average of Mom's height, plus 5 inches, and Dad's height.

(Thus my kid--the daughter of a 5-foot-7 mom and 6-foot-2 dad--should be 5-feet-8 as an adult.)

For another version of this method, go to www.cdc.gov/growthcharts and you'll find height charts for U.S. kids up to 20, an age when growth has generally stopped. From those charts, you can figure out each parent's height "percentile" (a measure comparing his or her height to that of others). Take the average of those two percentiles to figure out your own kid's likely percentile, and thus ... finally

Of course, we're not the exact same height as all our same-sex sibs. (I've got 3 inches on my older sis, for instance.) So this method only takes you so far.

Another method draws from lots of diligent labor in the first part of the 20th century: X-ray after X-ray of hundreds of children's wrist bones done at different stages of their young lives, enclosed in a hefty tome called the Greulich-Pyle "Radiographic Atlas of Skeletal Development of the Hand and Wrist."

(These are not the kinds of experiments one could do today, given the modern appreciation of the risks of repeated X-raying.)

The idea is that those little bones in the wrist slowly change as kids get older. Over time, they slowly "ossify"--turn from cartilage, basically, into proper hard bone visible on an X-ray film.

If a kid has suspected growth delays, an X-ray is taken and then the trusty Greulich-Pyle atlas is dragged down from some shelf, says Dr. Edward Reiter, pediatric endocrinologist at the Baystate Medical Center Children's Hospital in Springfield, Mass. That gives a sense of whether the child's "bone age" matches his or her age. That, in turn, allows one to calculate the years of bone growth a child has left--and thus how tall he or she's likely to end up.

This isn't totally iron-clad either, Reiter says. Different radiologists read the same X-rays differently. In fact, the same radiologist can read the same X-ray differently, as Reiter discovered years ago when he sent the same one for reading multiple times and got different answers.

Other growth tidbits:

* A plethora of chemicals--notably growth hormone--govern the rate at which we grow.

* Growth hormone gushes out in pulses, many times a day. The size of those pulses governs how fast we grow: Pulses are huge at puberty and wee dribbles in later years.

* We seem to grow in pulses too--in little spurts separated by periods of no growth.

* Growing pains--usually in the legs--are real, doctors say, but it's not known what causes them.

* Chronic sicknesses and malnutrition affect ultimate height, explaining why people in former centuries were shorter than they are today. (People in the U.S. are probably maxed out, height-wise.)

Puberty signifies the inevitable end of growth.

*

If you have an idea for a Booster Shots topic, write or e-mail Rosie Mestel at the Los Angeles Times, 202 W. 1st. St., Los Angeles, CA 90012, rosie.mestel@latimes.com.